Remove alloc-str in Hustle.

hustle/heap.rkt

@@ -1,5 +1,5 @@
 #lang racket
-(provide alloc-box alloc-cons alloc-str heap-ref heap-set)
+(provide alloc-box alloc-cons heap-ref heap-set)
 
 ;; Value* Heap -> Answer*
 (define (alloc-box v h)
@@ -11,11 +11,6 @@
   (cons (cons v2 (cons v1 h))
         (list 'cons (length h))))
 
-;; String Heap -> Answer*
-(define (alloc-str s h)
-  (cons (append (reverse (string->list s)) (list (string-length s)) h)
-        (list 'str (length h))))
-
 ;; Heap Address -> Value*
 (define (heap-ref h a)
   (list-ref h (- (length h) (add1 a))))